© Applied Science Innovations Pvt. Ltd., India
ASI
Carbon – Sci. Tech. 8/3(2016)1-7
Carbon – Science and Technology
ISSN 0974 – 0546
http://www.applied-science-innovations.com
RESEARCH ARTICLE
Received:10/3/2016, Accepted:15/04/2016
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Study of water tolerance in hydrous ethanol-gasoline blends
T. N. Sreenivasa(1), K. M. Harinikumar(2), Sathyanarayana. A.(3)
1) Department of Mechanical Engineering, AMC Engineering College, Bangalore, India.
2) Department of Plant Biotechnology, University of Agricultural Science , GKVK, Bangalore, India.
3) Department of Mechanical Engineering, Visvesvaraya Technological University, Belagavi, India.
Abstract: Water tolerance of ethanol-gasoline blends of various proportions is investigated using cosolvents such as TBA (tert-butyl alcohol), cyclohexane, heptane, acetone, iso-octane, and toluene at 300
K. Miscibility was studied using a simple experimental method for various proportions of water-ethanolgasoline blends with and without co-solvents. Results of water tolerance for each co-solvent are
presented in this paper for stable mixture at room temperature.
Keywords: Blended fuel, Co-solvents, Ethanol, Ethanol-gasoline, Hydrous ethanol, Oxygenates, Phaseseparation, Water-tolerance, and Wet ethanol.
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1. Introduction: In 1925, Ford told the New York Times reporter that ethyl alcohol was ―the fuel of the
future‖ [1]. Today, Ethanol is an octane booster and a potent oxygenate. Also, it has been in use for over
30 years in Brazil as a fuel. Use of ethanol results in reduction of greenhouse gas emissions, reduction in
carbon monoxide, reduction of oxides of nitrogen and un-burnt hydrocarbon emissions, increase in
combustion efficiency, reduction in fuel cost and provides rural employment [2]. Ethanol has replaced
other oxygenates such as MTBE (methyl-tertiary-butyl-ether)in many regions of the world. Other octane
boosting components are not environmentally friendly such as lead, an additive which is a toxic air
pollutant and poisons catalytic converter catalyst, benzene is carcinogenic, aromatics and olefins which
cause smog and MTBE is a potential ground water pollutant.
The use of ethanol and ethanol-gasoline blended fuel reduces dependence on imported oil and helps
mitigate increasing oil prices. Use of higher percentage of ethanol in gasoline blended fuel depends on
price of anhydrous ethanol. Large scale productions of ethanol from bio-refineries are from the
following biomass sources: corn, sugarcane and lingo-cellulosic biomass. Bio-conversion of starches to
sugars with enzymes, fermentation of sugars with yeast yields a mixture of ethanol and water, followed
by distillation and dehydration of ethanol [3]. Dehydration of ethanol amounts to 14% of the net energy
[4]. Therefore, use of hydrous ethanol drastically reduces the ethanol cost in hydrous ethanol-gasoline
blended fuel.
The use of hydrous ethanol-gasoline blended fuel has the following challenges:
 Phase separation: Forms two layers upon addition of very small amounts of water. Resulting in
loss of ethanol to aqueous phase and reduction in octane number of the blended fuel. Phase
separation is a serious technical problem associated with ethanol-gasoline blends [5].
 Volatility properties: Addition of ethanol to hydrocarbon significantly affects the volatility
properties. Commingling of ethanol fuel can potentially lead to off-spec gasoline [5].
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 Materials compatibility: Plastics, elastomers and non-metals are not recommended for use with
ethanol-gasoline blends due to problem of swelling [5].
 Corrosion: Corrosion in hydrous ethanol is of three types: General, Dry and Wet corrosion.
General corrosion is due to ionic impurities, dry corrosion is due to properties of ethanol, and wet
corrosion is caused by azeotropic formation of ethanol and water, which oxidizes most metals [2].
 Performance of the engine: Water-Ethanol phase may damage the engine due to lack of
lubrication.
Hydrous ethanol is a cheap alternative to anhydrous ethanol, but blending with gasoline can cause the
technical problem of phase separation, resulting in separation of heavier aqueous phase at the bottom
and an upper gasoline rich phase at the top. Ethanol mixes uniformly with gasoline, but upon addition of
small amount of water the ethanol-gasoline blend will absorb water due to hydrogen bonding of waterethanol molecules [5, 6]. When the amount of water added exceeds the solubility limit it separates into
ethanol-rich aqueous phase.
Water tolerance in blends is defined as the volume percentage of water that a blend can retain in
solution, i.e. ―tolerate‖ at a given temperature without phase separation [7]. Water tolerance can be
improved by adding co-solvents such as: TBA (tert-butyl alcohol), cyclohexane, heptane, acetone, isooctane, and toluene in hydrous-ethanol gasoline blends.
The addition of co-solvents can improve the water tolerance; a hydrous ethanol containing 5 vol% of
water can be used without the problem of phase separation at room temperature, i.e.25°C – 30°C. For
higher water content of 6- 10 vol% in ethanol i.e. wet ethanol, a biomass adsorption process needs to be
designed for dehydration of ethanol [3].
The aim of present study is to determine what proportion of water-ethanol-gasoline mixture with cosolvents will yield a stable mixture at room temperature.
2. Experimental:
Miscibility studies: The miscibility characteristic of hydrous ethanol was studied in two parts:
1. Water-Ethanol-Gasoline miscibility characteristic without co-solvents
2. Water-Ethanol-Gasoline miscibility characteristic with co-solvents
Part 1 of the experiment was studied for various proportions of water (1-5%vol) and anhydrous ethanol
(5-25%vol) in gasoline in trial 1-5 for temperatures: 4°C, 30°C, 35°C, 40°C, and 45°C. And trial 10-40
is the study of wet ethanol of various proportions of water (10-40%vol) and anhydrous ethanol (525%vol) in gasoline for temperatures: 4°C, 30°C, 35°C, 40°C, and 45°C.
Experimental set-up for Part 1 consists of prepared blended fuel in a glass beaker covered with
aluminum foil and stirred in a Magnetic stirrer with hot plate as shown in Figure 1. Temperatures were
set using switch in the Magnetic stirrer and were measured for the various trials using laboratory
thermometer. The sample was collected in a 50 ml graduated centrifugal tube and kept in the refrigerator
for observing phase separation at low temperature (4°C). Measurement of aqueous phase was observed
at regular intervals for various trials in 50 ml graduated centrifugal tube as shown in Figure 2.
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Carbon – Sci. Tech. 8/3(2016)1-7
Figure 1: Blended Fuel in the Magnetic Stirrer with hot plate for Part 1 experiment,
a 10 ml glass cylinder was used for Part 2 experiment.
Figure 2: Measurement of aqueous phase in 50 ml graduated centrifugal tube
Part 2 of the experiment was studied for various proportions of water (1-5 %vol) and anhydrous ethanol
(10-50 %vol) in gasoline with co-solvents (1-25 %vol) that is, Toluene, Cyclohexane, Heptane, IsoOctane, Acetone and TBA (t-butyl alcohol) at room temperature (300 K). One set of trial per co-solvent
was conducted for 1 %vol water, 10 %vol anhydrous ethanol, and 1-25 %vol co-solvent in gasoline at
room temperature (300K), and another set of trials was conducted keeping 10 %vol co-solvent fixed for
various proportions of water (1-5%vol) and anhydrous ethanol (10-50 %vol) in gasoline.
Experimental set-up for Part 2 is simple and rudimentary in approach, (see Figure 1). First, the blend is
prepared in a 10 ml graduated cylinder by first adding gasoline of given proportion and then adding cosolvents (1-25 %vol), anhydrous ethanol (10 %vol) and water (1 %vol) in gasoline at room temperature
(300 K). The second set of blend is prepared keeping the co-solvents proportion constant i.e. (10 %vol)
and by adding various proportion of water (1-5 %vol) and anhydrous ethanol (10-50 %vol) in gasoline at
room temperature (300 K).Any phase separation observed is noted with measurement of aqueous phase
in the 10 ml glass cylinder.
Properties of blended fuels and co-solvents: Anhydrous ethanol used in the experiment is absolute
ethanol (200 proof), Gasoline used is commercial gasoline purchased from Bharat Petroleum of
specification MS 91/MS 95 as per IS 2796-2008 for motor gasoline and water used in the experiment is
distilled/deionized water.
Co-solvents:
Toluene sulphur free, C7H8: Grade LS for synthesis (organic and inorganic)
Cyclohexane, C6H12: Grade LR for synthesis (organic and inorganic)
Heptane (Fraction from petroleum) 95%: Grade LR for synthesis (organic and inorganic)
Iso-Octane (2, 2, 4-Trimethylpentane, C8H18): Grade LR for synthesis (organic and inorganic)
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Acetone, C3H6O: Grade LR for synthesis (organic and inorganic)
TBA (tert-Butyl Alcohol, C4H10O): Extra-pure AR
The aim of blending co-solvents in ethanol-gasoline fuel is [8]:
 To improve solubility of water in ethanol-gasoline blend
 To help lower the phase separation temperature
 To reduce the transfer of ethanol to aqueous phase
Blending sample measurement: An adjustable volume pipettors (100 μl - 1000 μl) with disposable
plastic tips were used to blend samples of different samples based on following nomenclature: for
example, 1EW10CH1 represents 1 %vol of water, 10 %vol of ethanol and 1 %vol of cyclo-hexane (cosolvent) in gasoline. Similarly, 5EW10 represents 5 %vol of water and 10 %vol of anhydrous ethanol in
gasoline.
Experimental errors: Observations of phase separation were measured visually using the graduated glass
cylinder or centrifugal tube. There was loss of gasoline/ethanol vapour at temperatures above 30°C,
which is not accounted in the measurement. There was negligible change in phase separation at lower
temperatures, while observed in the refrigerator at 4°C. There could be errors in measurement based on
wait time for phase separation.
3. Results:
The results of Part 1 of the experiment i.e. without co-solvents showed that by adding water of 1%vol to
5%vol in various proportions of anhydrous ethanol (5-25%vol) and gasoline blends show phase
separation for temperatures: 4°C, 30°C, 35°C, 40°C, and 45°C. For higher concentration of water (1040%vol) high ethanol-rich aqueous phase was found in most samples resulting in ethanol-deficient
gasoline layer at the top of the sample as seen in figure 2. From the above experiments it clearly shows
that an ethanol-gasoline blend undergoing phase separation when small amount of water is added to the
blend has preferential partition for ethanol resulting in ethanol-rich aqueous phase at the bottom and
ethanol-gasoline phase at the top. The ethanol-rich aqueous phase observed during the experiments had
larger share of the volume which may be due to aromatic hydrocarbons in commercial gasoline that are
soluble in ethanol when adding water of higher concentration.
The results of Part 2 of the experiment with co-solvents showed that by adding water of 1 %vol in 10
%vol anhydrous ethanol for various proportions of co-solvents (1-25 %) in gasoline resulted in phase
separation for the following co-solvents at 300 K: Toluene, Cyclohexane, Heptane, Iso-Octane and
Acetone. However, co-solvents TBA (tert-Butyl Alcohol) showed promising water tolerance for the
following samples: 1EW10TBA20 (i.e. 10 %vol ethanol and 20 %vol TBA in gasoline) and
1EW10TBA25 ((i.e. 10 %vol ethanol and 25 %vol TBA in gasoline) showed 1%vol water tolerance as
shown in Table 6.
Table 1-6 below shows water tolerance of different co-solvents used of 10 %vol in various proportion of
anhydrous ethanol (10-50 %vol) in gasoline at 300 K. The results showed that water tolerance of 1-5
%vol were achieved at higher concentration of anhydrous ethanol in gasoline blend i.e. 50 %vol of
anhydrous ethanol for the following co-solvents as shown in the Table 1-4 for Toluene, Cyclohexane,
Heptane and Iso-Octane. The water tolerances of 1-5 %vol were achieved at 30-40 %vol of anhydrous
ethanol for Acetone and TBA. The water tolerance of 1%vol was only achieved for 10 %vol anhydrous
ethanol with higher concentration of TBA, i.e. 20-25 %vol TBA in ethanol-gasoline blends as shown in
Table 6. The number of replications done for each stable sample was three. The results presented below
(Table 1-6) are for the samples which showed stable mixture without phase separation at room
temperature (300K).
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Carbon – Sci. Tech. 8/3(2016)1-7
Table 1: Experimental results of Toluene at 300 K.
Sample
1EW40T10
5EW50T10
Toluene vol%
10
10
Ethanol vol%
40
50
Water tolerance vol%
1
5
Table 2: Experimental results of Cyclohexane at 300 K.
Sample
Cyclohexane
vol%
10
4EW50CH10
Ethanol vol%
Water tolerance vol%
50
4
Table 3: Experimental results of Heptane at 300 K.
Sample
5EW50H10
Heptane vol%
10
Ethanol vol%
50
Water tolerance vol%
5
Table 4: Experimental results of Iso-Octane at 300 K.
Sample
5EW50IO10
Iso-Octane vol%
10
Ethanol vol%
50
Water tolerance vol%
5
Table 5: Experimental results of Acetone at 300 K.
Sample
1EW30A10
2EW40A10
5EW50A10
Acetone vol%
10
10
10
Ethanol vol%
30
40
30
Water tolerance vol%
1
2
5
Table 6: Experimental results of TBA (tert-Butyl Alcohol) at 300 K
Sample
1EW10TBA20
1EW10TBA25
2EW30TBA10
5EW40TBA10
5EW50TBA10
TBA vol%
20
25
10
10
10
EtOH vol%
10
10
30
40
50
Water tolerance vol%
1
1
2
5
5
As can been seen, the above results show that TBA is effective at improving water tolerance in
comparison to other co-solvents. The results follow the trend citied by other researches in the literature.
Rajan et al. [9-10] investigated the amount of water in ethanol that can be tolerated before phase
separation. The blends obtained from the study were referred as ―limit blends‖, since these were the
limits characterizing the miscibility of water-ethanol-gasoline blend. Gramajo de Doz et al. [6] studied
water tolerances and ethanol concentrations at equilibrium in the upper gasoline-rich phase for several
gasoline-ethanol-water multi-component systems at temperatures of 283.15, 293.15 and 313.15 K.
Osten, David W et al. [11] studied phase separation at low temperature by varying the percentage of
blending agents such as TBA(ter-Butyl alcohol) and IPA (isopropyl alcohol).
4 Discussion: The experimental methods used here in the study are similar to a classroom
demonstration of water induced phase separation of alcohol-gasoline blends [12]. This simple method of
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Carbon – Sci. Tech. 8/3(2016)1-7
demonstration can help us discuss the most serious problem associated with ethanol-gasoline blends
such as i) ethanol-water phase separation and ii) properties of mixtures- solubility.
As can be seen, from the above experiment that addition of small amount i.e.0.1 ml (1 %vol) of distilled
water in ethanol-gasoline blends results in phase separation. However, our aim of using hydrous ethanol
as a cheap alternative fuel without phase separation requires the understanding of partition preference of
ethanol into the aqueous phase and the tie-line in the ternary phase diagram for ethanol-gasoline-water
mixture [5, 12-14]. Blending hydrous ethanol-gasoline blend with blending agents i.e. co-solvents at
higher temperatures might partially solve the problem for water content of 1-5%vol and blending agent
such as TBA (tert-butyl alcohol) certainly improves the water tolerance at higher concentration of TBA.
But for higher concentration of water (10 %vol) in ethanol and for hydrous ethanol-gasoline blend at
lower temperatures it might require a solution outside the ternary phase diagram for ethanol-gasolinewater. One of the possible avenues is dehydration of ethanol using fixed bed biomass adsorption, which
needs to be explored [15].
Acknowledgement: The authors would like to thank University of Agricultural Sciences (GKVK),
Bangalore for supporting research in the area of biofuels by providing the Bio-fuel lab and the required
necessary infrastructure to conduct the experiments. We also wish to thank Visvesvaraya Technological
University, Belgaum for encouraging research in biofuels.
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